Dispersion strengthening of metals by internal oxidation

ABSTRACT

Disclosed are methods and compositions for forming dispersionstrengthened metal products by the in situ internal oxidation of an alloy powder of a solute metal in a matrix metal. The matrix metal is relatively noble with respect to the solute metal so that the solute metal will be preferentially oxidized. The oxidant for the internal oxidation of said alloy powder is a mixture of a heat-reducible (i.e., reducible by the solute metal with heat) metal oxide (the metal moiety of which is different or the same as the matrix metal that is present in the alloy) present in proportion sufficient for substantial oxidation of all of said solute metal to solute metal oxide; and a hard, refractory metal oxide (the metal moiety of which is different from or the same as the solute metal present in the alloy). The alloy powder and the oxidant are intimately mixed and heated in an inert atmosphere for internal oxidation. Upon internal oxidation, the composite residue of spent oxidant comprises an in situ heat-reduced metal intimately associated with the refractory metal oxide, and such residue is coalesced with the rest of the mass by hot working.

[ Dec. 18, 1973 DISPERSION STRENGTHENING OF METALS BY INTERNAL OXIDATION[75] Inventors: Anil V. Nadkarni, Glen Burnie;

Erhard Klar, Pikesville, both of Md.

[73] Assignee: SCM Corporation, Cleveland, Ohio [22] Filed: Jan. 13,1972 [21] Appl. No.: 217,506

.. 75/2ll X 3,505,059 4/1970 Cerulli 3,552,954 l/l97l McDonald 3,179,5154/1965 Grant et al .1 .1 75/206 FOREIGN PATENTS OR APPLICATIONS 932,4607/1963 Great Britain 75/206 919,052 2/l963 Great Britain 1111 75/206669,315 8/I963 Canada 75/206 Primary Examiner-Carl D. QuarforthAssistant Examiner-R. E. Schafer Atrorney-Merton H. Douthitt et al.

[57] ABSTRACT Disclosed are methods and compositions for formingdispersion-strengthened metal products by the in situ internal oxidationof an alloy powder of a solute metal in a matrix metal. The matrix metalis relatively noble with respect to the solute metal so that the solutemetal will be preferentially oxidized. The oxidant for theinternal'oxidation of said alloy powder is a mixture of a heat-reducible(i.e., reducible by the solute metal with heat) metal oxide (the metalmoiety of which is different or the same as the matrix metal that ispresent in the alloy) present in proportion sufficient for substantialoxidation of all of said solute metal to solute metal oxide; and a hard,refractory metal oxide (the metal moiety of which is different from orthe same as the solute metal present in the alloy). The alloy powder andthe oxidant are intimately mixed and heated in an inert atmosphere forinternal oxidation, Upon internal oxidation, the composite residue ofspent oxidant comprises an in situ heat-reduced metal intimatelyassociated with the refractory metal oxide, and such residue iscoalesced with the rest of the mass by hot working.

18 Claims, 3 Drawing Figures 40/ 512 DIEPERfi/ON 5T/2EN6THENED WITH A220(EXAMPLE 1) ANNEAL/NG TEMP. F HR. 0/ ARGO/V IMENTEUBECW r973 3.779.714

JLL

ELEMENTAL ALUM/NUM BY W7.

0.254 0.4173 ae'e/ 0.650 /.o'40 722 0 42 0 BY wr Fig. 3

DISPERSION STRENGTHENING OF METALS BY INTERNAL OXIDATION The presentinvention relates to dispersion strengthening of ductile matrix metalsby the in situ formation of a hard, refractory oxide phase therein bythe technique known as internal oxidation. Dispersionstrengthened metalproducts such as copper dispersion strengthened with aluminum oxide havemany commercial and industrial uses where high temperature strength andhigh electrical conductivity and/or heat conductivity are desired orrequired. Such uses include frictional brake parts such as linings,facings, drums and the like and other machine parts for frictional applications; contact points for resistance welding elec trodes;electrodes generally, electrical switches and electrical switch gears,transistor assemblies, wires for solderless connections, wires forelectrical motors and many other related applications.Dispersionstrengthened products of this invention are useful in theabove and other applications.

In the past, it has been recognized that strength and hardness can beimparted to a solid solution alloy of a ductile matrix metal, havingrelatively low negative heat or free energy of oxide formation, and asolute metal having a relatively high negative heat or free en ergy ofoxide formation, by heating the alloy under oxidizing conditions so asto preferentially oxidize the solute metal to cause the in situprecipitation of hard, refractory solute metal oxide particles in thematrix metal without substantial oxidation of the matrix metal. Thistechnique is known as the in situ internal oxidation of the solute metalto the solute metal oxide or more simply internal oxidation. In internaloxidation, the matrix metal is relatively noble compared to the solutemetal so that the solute metal will be preferentially oxidized.

In the past, attempts have been made to dispersion strengthen alloys byinternal oxidation in various ways. For instance, U. S. Pat. No.3,026,200 shows the surface oxidation of alloy powder followed by a heattreatment in an inert atmosphere to diffuse the oxygen from the surfaceof the alloy and to preferentially oxidize the solute metal to solutemetal oxide within the alloy. This method requires the precise controlof the conditions for oxidation of the alloy powder.

U. S. Pat. No. 3,399,086 discloses the internal oxidation ofcopper-aluminum alloy in plate or strip form using copper oxide as theoxidant, through an oxidation-reduction chemical mechanism. The copperoxide is reduced and gives up its oxygen for the preferential oxidationof the alloyed aluminum to form dispersed particles of aluminum oxidedispersed within the copper matrix. Internal oxidation of alloy powderis not discussed, so the problem of oxidant powder removal from alloypowder is not a factor.

U. S. Pat. No. 3,184,835 discusses the internal oxidation ofcopper-beryllium or copper-aluminum alloys wherein th id atis situateand milled mesh) mixture consisting of 50 percent copper oxide and 50percent aluminum oxide. The use of the sintered mixture as the oxidantis said to minimize adhesion of the oxidant residue to the internallyoxidized alloy. The sintcred oxidant residue is physically separatedfrom the internally oxidized alloy powder before the powder is formedinto a dispersion-strengthened metal product.

U. S. Pat. No. 3,179,515 discloses the internal oxidation of alloys bysurface oxidizing a powdered alloy and then diffusing the oxygen intothe powder particles to preferentially oxidize the solute metal tosolute metal oxide. This patent shows that internal oxidation can beachieved by treating the alloy powder at a controlled partial pressureof oxygen at which copper does not readily oxidize whereas the solutemetal is oxidized mainly by diffusion of oxygen into the alloy. Particlesize and surface parameters of the solute metal oxide are said to becritical to product performance.

British Patent 654,962 shows a method of internally oxidizing silver,copper and/or nickel alloys containing solute metal by oxygen diffusionto increase the hardness of the alloy by more than 30 percent.

All of these prior art methods either require a delicate control overthe partial pressure of oxygen during internal oxidation or the removalof oxidant residue after the internal oxidation reaction is complete.When an oxidizing gas is used as an oxidant, elaborate processing andcontrol equipment must be provided and maintained. When the oxidant isan oxide of the matrix metal or another metal the reduced oxide metaloften sinters during the oxidizing reaction and produces agglomeratesthat must be separated and removed before the metal powder can befurther processed. Furthermore, any oxidant residue that remains in theinternally oxidized powder in these prior art processes forms defectsdue to compositional variations when said metal shapes are eventuallyformed. The present invention provides a unique solution to this problemin providing for the complete assimilation of the oxidant residue intometal articles formed from the internally oxidized alloy powder.

The above and other advantages will be more easily understood from thefollowing description and draw' ings wherein FIGS. 1, 2 and 3 are graphsshowing how the electrical conductivity, ultimate tensile strength andhardness vary with composition and annealing treatment according to thepresent invention.

In achieving the objects of the present invention, one feature providesfor the internal oxidation of solute metal to solute metal oxide in apowdered alloy of a matrix metal and solute metal wherein the matrixmetal has a negative free energy of oxide formation per gram atom ofoxygen at 25C. ranging up to kilocalories per gram atom of oxygen at25C.; and the negative free energy of formation of said solute metaloxide exceeds the negative free energy of formation of said matrix metaloxide by at least 60 kilocalories per gram atom of oxygen at 25C. in thepresence of and in intimate admixture with an oxidant comprising apulverulent, in situ, heat-reducible metal oxide having a negative freeenergy of oxide formation per gram atom of oxygen ranging up to 70kilocalories per gram atom of oxygen at 25C. in intimate interspersionwith discrete particles of hard, refractory metal oxide, the negativefree energy of formation of said hard, refractory metal oxide exceedingthe negative free energy of formation of said heat-reducible metal oxideby at least 60 kilocalories per gram atom of oxygen at 25C. Theheatreducible metal oxide can contain the same or different metal moietythat is present as the matrix metal in the alloy. Similarly, the hard,refractory metal oxide that is present in a proportion and particle sizeadapted for dispersion strenghtening the oxidant residue resulting frominternal oxidation can be the same or different metal oxide that resultsfrom the internal oxidation of the solute metal to the solute metaloxide in the alloy.

The pulverulent, in situ heat-reducible metal oxide in the oxidant is insubstantial stoichiometric proportion for internal oxidation of all thesolute metal to solute metal oxide in said alloy. After internaloxidation, the oxidant residue comprises uniformly distributedagglomerates consisting of particles of in situ reduced metal andparticles of hard, refractory metal oxide. The oxidant residue is inintimate mixture with the particles of internally oxidized alloy powderwhich after internal oxidation comprises matrix metal containingdispersed particles of refractory oxide. According to this presenttechnique, the oxidant is neither presintered nor is the oxidant residueseparated from the internally oxidized alloy powder as in U. S. Pat. No.3,184,835. When the internally oxidized alloy powder and the oxidantresidue are eventually consolidated by hot working to form a solid metalworkpiece, the oxidant residue itself dispersion strengthens to form anintegral part of the resulting workpiece.

Preferably, the in situ heat-reducible metal oxide in the oxidantcontains the same metal moiety as the matrix metal in the alloy powder;and preferably, the hard, refractory metal oxide in the oxidant containsthe same metal moiety as the solute metal in the alloy powder. in oneparticular commercially important embodiment of this preferred practice,the oxidant contains substantially the same proportion of matrix metalmoiety and solute metal moiety as are present in the alloy powder. Thusupon eventual coalescense of the internally oxidized mixture of alloyand oxidant residue into a workpiece, the oxidant residue itself is ofsubstantially the same composition as the internally oxidized alloy andbecomes dispersion strengthened therewith.

Another feature of the present invention resides in a metal powdercomposition based upon an alloy of matrix metal and solute metal about0.01 to 5 percent by weight, adapted for coalescense upon hot working toform dispersion-strengthened metal articles, said composition comprisingparticles of internally oxidized alloy of a matrix metal whose oxide hasa negative free energy of formation at 25C. ranging up to about 70kilocalories per gram atom of oxygen, the matrix metal having dispersedsubstantially uniformly throughout by internal oxidation fine particlesof a hard, refractory solute metal oxide, the negative free energy offormation of said solute metal oxide exceeding the negative free energyof oxide formation of said matrix metal by at least 60 kilocalories pergram atom of oxygen at 25C., said particles of internally oxidized alloybeing blended with an oxidant residue mixture comprising discreteparticles of in situ heat-reduced metal having a negative free energy ofoxide formation at 25C. ranging up to 70 kilocalories per gram atom ofoxygen and discrete particles of hard, refractory metal oxide having anegative free energy of oxide formation exceeding the negative freeenergy of formation of said heat-reduced metal by at least 60kilocalories per gram atom of oxygen at 25C. Preferably, theheat-reduced metal oxide in the oxidant residue is of the same metalmoiety as the matrix metal in the internally oxidized alloy. Mostpreferably, the proportion of matrix metal and hard, refractory metaloxide in said oxidant residue is substantially the same as theproportion of matrix metal and solute metal oxide in said internallyoxidized alloy.

The matrix metals in the alloy and in situ, heatreduced metal in theoxidant residue are defined broadly as those metals having a meltingpoint of at least about 200C. and whose oxides have a negative freeenergy of formation at 25C. of from 0 to kilocalories per gram atom ofoxygen. Suitable metals of this class for practicing the presentinvention include the following:

Approximate negative free energy of formation of oxide at 25C. in kilo-Matrix metal Hcat'reducible In the above table, matrix metal of thealloys and in situ heat-reduced metal of the oxidant residue are shownto be of the same class of metals. Similarly, the correspondingheat-reducible metal oxides in the oxidant and matrix metal oxides arelisted as the same class of metal oxides.

In practicing the present invention, a matrix metal and a solute metalare alloyed by conventional techniques such as melting the metals underinert or reducting conditions. The matrix metal of the alloy can be asingle matrix metal of a combination of two or more matrix metals whichthemselves form an alloy. Accordingly, the term matrix metal includes aplurality of matrix metals so alloyed. Similarly, the solute metalincludes a single solute metal or a combination of two or more solutemetals which form solid solution alloys with the matrix metal. The alloycomposition comprises 0.01 percent to about 5 weight percent of thesolute metal with the balance of the alloy being matrix metal with orwithout other conventional additives in minor proportions to improveabrasion resistance, hardness, conductivity and otherselectedproperties.

The alloy is then comminuted by atomization or other conventional sizereduction techniques such as grinding or ball milling to form aparticulate alloy having an average particle size of less than about 300mi crons, usually less than about microns and preferably less than about44 microns.

Optionally, the comminuted alloy powder is then annealed according toconventional procedures to increase the grain size since one of theproblems associated with internal oxidation of alloys is the tendencyfor the solute metal oxide to concentrate at the powder grainboundaries. This is undesirable because it can cause early failure understress at these grain boundaries. It is, therefore, often desirable toreduce the grain boundary area in the alloy powder; and this is done byannealing the powder to form a larger grain size of at least about ASTMGrain Size Number 6 as measured by ASTM Test E-l 12. For copper-aluminumalloys which are one of the more commercially important embodiments ofthe present invention, annealing treatment at 1,600F. for one hour in aninert atmosphere such as argon produces grain size of at least aboutASTM Grain Size Number 6 by ASTM Test El 12.

The oxidant for internally oxidizing the above alloy powder is a mixtureof an in situ heat-reducible metal oxide (this term includes materialscapable of providing such metal oxide under internal oxidationconditions) and a hard, refractory metal oxide. The heat reducible metaloxide in the oxidant is in substantially stoichiometric proportion forinternally oxidizing all of the solute metal in said alloy.

In any particular combination of matrix metal and solute metal in thealloy to be internally oxidized, the matrix metal must be relativelynoble with respect to the solute metal so that the solute metal will bepreferentially oxidized. This is achieved by selecting the solute metalsuch that its negative free energy of oxide formation at 25C. is atleast 60 kilocalories per gram of oxygen greater than the negative freeenergy of formation of the oxide of the matrix metal at 25C. Generally,such solute metals have a negative free energy of oxide formation pergram atom of oxygen of over 80 kilocalories and generally over 120kilocalories. The approximate negative values of free energy offormation of several suitable solute metal oxides at 25C. are:

Approximate negative free energy of formation of oxide at 25C. inkilocalories per gram Solute metal oxide and hard, refractory Solutemetal metal oxide atom of oxygen Silicon SiO, 96 Titanium TiO, 101Zirconium ZrO, 122 Aluminum A1 0, 126 Beryllium 81:0 139 Thorium Th0,146 Chromium Cr 0 83 Magnesium MgO I36 Manganese MnO 87 Niobium w o, 85Tantalum Ta O 92 Vanadium V0 99 In the above table, the solute metaloxide in the alloy and hard, refractory metal oxide in the oxidant areshown to be the same class of metal oxides.

The metal moiety of the heat-reducible metal oxide in the oxidantpreferably is the same metal as matrix metal present in the alloy to beinternally oxidized, although the heat-reducible metal oxide moiety canbe different to achieve specific performance requirements in the finalproduct.

For instance, alloy matrix metal/oxidant heatreducible metal oxidecombinations include:

Oxidant Heat-Reducible Alloy Matrix Metal Metal Oxide copper cobaltoxide, nickel oxide, copper oxide nickel cobalt oxide, nickel oxide,copper oxide cobalt cobalt oxide, nickel oxide, copper oxide Similarly,the hard, refractory metal oxide in the oxidant preferably is the sameas the solute metal oxide formed in the alloy during internal oxidationof the al- Oxidant Hard, Refractory Alloy Solute Metal Oxide Metal OxideAlgoq Al,0,, BeO, ZrO,, Th0 BeO A1 0,, BeO, ZrO,, Th0 ZrO, Al,O,, BcO,ZrO, Th0, Th0, Al,O,, BeO, ZrO:, Th0,

To achieve the proper proportion of oxidant, about 0.1 to about 10 partsby weight of oxidant are em ployed per parts of alloy to be internallyoxidized. The exact proportions depend on the solute metal'to beoxidized, its concentration in alloy and oxygen content of oxidant.

In a commercially important embodiment, the matrix metal is copper andthe solute metal is aluminum in the alloy; and the oxidant containscopper oxide as the in situ, heat-reducible metal oxide and aluminumoxide as the hard, refractory metal oxide. The copper oxide in theoxidant is present in substantially stoichiometric proportions forinternally oxidizing all of the aluminum metal to aluminum oxide in thealloy powder. During internal oxidation of the preferred embodiment, thein situ, heat-reducible copper oxide in the oxidant gives up its oxygento the aluminum metal in the alloy. This reduces the copper oxide tocopper in the oxidant which by virtue of its intimate mixture withaluminum oxide in the oxidant becomes dispersion strengthened duringsubsequent coalescense upon hot working. The stoichiometry of theoxidant is predetermined so that the composition of the oxidant residueand internally oxidized alloy are substantially identical after internaloxidation. This represents a substantial advance over the prior arttechniques where matrix metal oxide alone is used as the oxidant andreverts to matrix metal which must be removed, or where the mixture ofmatrix metal oxide and refractory oxide, because of unfavorable particlesize and homogeneity, does not produce acceptable properties.

The ratio of the average particle size diameters of the alloy particlesto the oxidant particles should be at least about 2:1 and usuallybetween about 5:1 and about 30:1 or even higher if practical to providedesirable inter-particle contacts for efficient chemical reaction and tomaximize the homogeneity of the final product. This particle sizedifi'erential permits the oxidant particle to surround the alloyparticle thus providing for suffieient solid-state reaction during theinternal oxidation period. Generally the oxidant particles are micron orsubmicron in particle size.

There are several methods of forming oxidant suitable for the presentinvention. In one method, an oxideforming salt of a refractory metal isapplied to and decomposed on a particle of a heat-reducible metal oxidein the micron or submicron range. In the case of the copper-aluminumsystem, for instance, submicron cuprous/cupric oxide particles aretreated with an aqueous solution of aluminum nitrate so as to form auniform coating. The particles are dried and heated to decompose thealuminum nitrate to form cuprous/cupric oxide particles having uniformcoating of aluminum oxide thereon. The amount of aluminum nitrate addedto the cuprous/cupric oxide particles is predetermined according to thealuminum oxide content desired in the final product.

In another method, oxide-forming compounds of refractory metal andmetals of heatreducible metal oxides are simultaneously coprecipitatedfrom solution of their salts. In the copper-aluminum system for example,copper and aluminum hydroxides or carbonates are precipitated from asolution of their nitrates by adding ammonium hydroxide or carbonaterespectively. The hydroxide and carbonate salts are then decomposed totheir respective oxides by heating.

In a third method, a physical blend of micron or submicron particles ofheat-reducible metal oxide and refractory oxide particles can beintimately blended in a blending device to form the oxidant.

The amounts of such oxidants that are to be added to the alloy aredetermined by the stoichiometric amount of oxygen required to oxidizethe solute metal completely. For most applications, this is in the rangeof 0.1 to parts oxidant per 100 parts of alloy. The percent of hard,refractory metal oxide in the oxidant is then calculated to produce thatdesired in the oxidant residue which also equals that desired in thefinal product.

In the following examples, all parts are parts by weight and alltemperatures are in F. unless stated otherwise.

EXAMPLE 1 Part A Preparation of the Alloy Powder Electrolytictough-pitch grade copper rods are melted in an inert refractory cruciblein an inductionheating furnace under reducing conditions at about2,300F. Metallic aluminum shavings are introduced into the molten copperin the-proportion of 0.33 percent by weight of the resulting moltenmetallic mass.

The molten solution of aluminum in copper is then super-heated to2,400F., atomized through an atomizing aperture in a jet of nitrogen(alternatively other inert gases or water or stream can be used as theatomizing fluid) to yield an atomized copper-aluminum alloy powder whichsubstantially all passes a l00-mesh U. S. Sieve indicating that theaverage particle size is less than about 146 microns.

The atomized and screened alloy powder is annealed at a temperature ofabout 1,600F. about an hour in an inert argon atmosphere to yield agrain size in the annealed powder of at least about ASTM Grain Size 6according to ASTM Test E-l 12. Preferably, the grains are as large aspossible to minimize grain boundary area in the powder. The alloy powderis then ready for use in combination with the oxidant.

Part B Preparation of the Oxidant One hundred parts of commerciallyavailable cuprous oxide (Cu- O) with an average particle size of about 1to 2 microns is mixed with 4.1 parts of a 20 percent aqueous solution ofAL(NO 911 0 to form a slurry of cuprous oxide in aluminum nitratesolution. The solution of aluminum nitrate is slurried with cuprousoxide particles, and the stirring is continued with mild heating at200F. until the water has evaporated and the mixture is almost dry. Themixture is then heated at a temperature of about 500F. for *7; hour todecompose the aluminum nitrate into aluminum oxide. The resultingagglomerate is then ground to form fine oxidant powder which passes a325-mesh sieve. The resulting oxidant powder comprises 99.44% Cu O and0.56% A1 0 by weight.

Part C Preparation of the Internally Oxidizable Alloy Powder-oxidantMixture The alloy powder of Part A is thoroughly mixed with the oxidantpowder of Part B in the proportion of 2.12 parts of oxidant to parts ofalloy powder. The mixing is accomplished in a ball-mill, although aconventional V-cone blending device can alternatively be used.

Part D Internal Oxidation of the Alloy Powder- Oxidant Mixture to formthe Internally Oxidized Metal Powder Composition The alloypowder-oxidant mixture of Part C is then charged to an internaloxidation vessel which is then sealed. The oxidation vessel is copper orcopper-lined steel to avoid contamination of the alloy powder oxidantmixture during oxidation.

The alloy powder-oxidant mixture is then brought to a temperature ofabout 1,750F. and maintained at this temperature for about 30 minutes toeffectuate internal oxidation of the alloy powder. Alternatively, theinternal oxidation can be carried out on a continuous basis using acontinuous belt furnace maintained under an inert atmosphere.

At the end of the 30-minute internal oxidation period, substantially allof the aluminum in the alloy powder has been oxidized to A1 0 andsubstantially all of the cuprous oxide in the oxidant has been reducedto metallic copper. The particles of internally oxidized alloy comprise99.37 percent by weight of copper plus minor amounts of impurities and0.63 percent by weight of A1 0 The oxidant residue comprises 99.37percent copper particles and 0.63% A1 0 particles. The overallinternally oxidized metal powder composition comprises 98.21 percentinternally oxidized alloy powder and 1.79 percent oxidant residue.

Part E Reduction of the Internally Oxidized Metal Powder Composition Theinternally oxidized metal powder composition of Part D is then placed ina reducing atmosphere of hydrogen at a temperature of about 1,500F. forone hour to reduce any residual copper oxide.

Part F Thermal Coalescence or Consolidation of the Internally OxidizedMetal Powder Composition The internally oxidized and reduced metalpowder composition of Part E are then charged under an inert argonaatmosphere to a thin-walled copper can having a diameter of about 7inches and equipped with a vent tube. The can and its contents areheated to about 1,600F. and the vent tube sealed. Alternatively insteadof using the inert gas atmosphere, the vent tube can be attached to avacuum pump; and the can is evacuated while the temperature of the canis brought to 1,600F. to remove any occluded gas from the powder. Afterevacuation at a pressure of l X 10 mm of Hg for 60 minutes at 1,600F.,the vent tube is sealed and disconnected from the vacuum pump.

The sealed can is brought to 1,700F. and then placed in a ram-typeextrusion press and is extruded to form extrudate in the shape ofcylindrical bar stock having a diameter of about 1.25 inches. Thiscorresponds to an extrusion ratio of about 31:1 (i.e., the ratio of thecross-sectional area of the can to the ratio of the cross-sectional areaof the extrudate).

The bar stock comprises about 99.37 percent copper having dispersedthroughout 0.63 percent (or about 1 .5 percent by volume) of A1 0particles and has a density of about 99.2 percent of the theoreticaldensity. The

bar stock has an electrical conductivity of 88% IACS* (*InternationalAnnealed Copper Standard A copper wire 1 meter long weighing 1 gram,having a resistance of 0.15328 ohms. at 20C. has a conductivity of 100%lACS. (see Kirk-Othmer: Encyclopedia of Chemical Technology, SecondEdition, Volume VI, Interscience Publishers, Inc. 1965 p. 133).), atensile strength of about 72,000 psi, an elongation of 19 percent usingASTM Test E-8 (for a test specimen 0.16 inch diameter and 0.65 inch gagelength) and a Rockwell hardness of about 75 units on the B scale. Allproperty measurements reported in the example are conducted at roomtemperature. The bar stock is substantially uniform and does not possessthe compositional defects that normally result when the spent oxidant ispresent in the dispersion-strengthened workpiece.

The bar stock is suitable for use as is, or it can be cold worked byswaging, forging, rolling, wire drawing, cold extrusion or cold drawingto form workpieces having particular tensile strengths according toconventional cold working techniques.

For instance, when the bar stock is reduced to 50 percent incross-sectional area by coldswaging, the tensile strength is 80,000 psi,the elongation is 13 percent and Rockwell B hardness is 84 units andconductivity is 86 percent IACS.

This swaged material with a Rockwell B hardness of 84 units and preparedby the procedure of Example 1 is annealed along with a commercialcopper-chromium alloy (0.9% Cr) at various temperatures for 1 hour inargon. The hardness values obtained by annealing in an annealing furnacefor 1 hour at the various temperatures and cooling to room temperatureafter annealing at each temperature are shown in FIG. 1. In anotherexperiment these same two materials are annealed together at 1,000F. inargon. At various time intervals samples are removed from the annealingfurnace, cooled at room temperature and tested for hardness. The resultsare shown in FIG. 2. The results shown in FIGS. 1 and 2 show thesuperior resistance to softening on heating of thedispersion-strengthened workpieces of this invention.

EXAMPLE 2 The procedures of Example 1 are repeated except that in Part Fthe 7 inch diameter copper can is replaced by a 1.25 inch diametercopper can. The extrusion is carried out at an extrusion ratio of 30:1yielding a 0.250 inch diameter rod. Such rod has an electricalconductivity of 86.7% IACS, a tensile strength of about 73,000 psi andan elongation of 19.8 percent in a gage length of 0.650 inch.

EXAMPLE 3 The material of Part E of Example 1 is fed into a thinwalledcopper can of 1.25 inch diameter and extruded at an extrusion ratio of45:1 to yield a rod of 0.206 inch diameter. This rod has an electricalconductivity of 89% IACS and when swaged and drawn to a 0.010 inchdiameter wire and heat treated at 500C. for f. hour in helium yields anultimate tensile strength of 84,000 psi, yield strength of 71,200 psiand an elongation of about 5 percent in inches.

EXAMPLE 4 The procedures of Example 2 are repeated except that thecompositions of the alloy powder in Part A and the oxidant in Part B ismodified so that the alloy powder and the oxidant each contain theequivalence of 0.22 weight percent aluminum to produce extruded copperbar stock containing 0.42 weight percent (or 1 volume percent) A1 0 Theelectrical conductivity of the bar stock is 91% IACS, the tensilestrength is 70,000 psi, elongation is 21 percent and the Rockwell Bhardness is 68 units. The bar stock is substantially uniform and doesnot possess the compositional defects normally associated with in situ,reduced copper oxide.

EXAMPLE 5 The procedures of Example 2 are repeated except that thecompositions of the alloy powder in Part A and the oxidant in Part B aremodified so that the alloy powder and the oxidant each contain theequivalence of 0.66 weight percent aluminum to produce extruded copperbar stock containing 1.26 weight percent (or 1 volume percent) A1 0 Theelectrical conductivity of the bar stock is 78% IACS, the tensilestrength is 85,000 psi, elongation is 19 percent and the Rockwell Bhardness is 89 units. The bar stock is substantially uniform and doesnot possess the compositional defects normally associated with in situ,reduced copper oxide.

FIG. 3 shows a plot of properties against aluminum or aluminum oxidecontent of workpieces as extruded in rod form as described in thisExample 5 and the preceding Examples 3 and 4.

EXAMPLE 6 The procedures of Example 1 are repeated except that the alloypowder of Part A has a particle size passing a U. S. standard sieve of80 mesh but is retained on a 325-mesh sieve. On the basis of the sievesemployed, the particle size varies between 44 and microns. Theinternally oxidized powder is used to compact test bars at 45 tsi havinga size of 0.394 in. X 0.394 in. X 2.96 in. These test bars are preheatedin an atmosphere of 92% N 8% H at 1,700F. for 10 minutes and forgedusing a 200 ton drop hammer and a 28 inch vertical drop rather thanextruded as in Example 1 Part F. The resulting drop-forged bars are 0.35inch square in cross-section The bars are then cold forged at roomtemperature to form 0.31 inch diameter bars which represents a 38percent reduction in cross-section.

The resulting test bars have a Vickers hardness (at 15 gram load) of 149Kg/mm a tensile strength of 67,700 psi and an elongation of 4.3 percent.The test samples are then annealed for 1 hour at 1,500F. in argon afterwhich the Vickers hardness is 139 Kg/mm tensile strength is 60,200 psiwith an elongation of 5.7 percent.

EXAMPLE 7 The procedures of EXAMPLE 6 are repeated except that the alloypowder has a particle size passing a U. S. standard sieve of 325 mesh.This means that the average particle is less than 44 microns. The testsample has a Vickers hardness of 153 Kg/mm, a tensile strength of 75,600psi and an elongation of 6.2 percent. After annealing in argon at1,500F. for 1 hour, the Vickers hardness is 153 Kglmm the tensilestrength is 68,000 psi and the elongation is 8.8 percent.

Examples 6 and 7 illustrate that the smaller alloy particles afterinternal oxidation produce better hardness, higher tensile strength andbetter elongation properties in the dispersion-strengthened product.

Examples 8 through 17 further illustrate the dispersion strengthening ofmatrix metals with various solute metal oxides by internal oxidation.Where solubility permits, the solute metal concentration in the alloy isselected to provide approximately percent by volume of the solute metaloxide. In cases where the solubility of the solute metal is notsufficient to provide 5 percent by volume of the solute metal oxide, thesolute metal concentration in the alloy is adjusted to maximumsolubility at room temperature. In all of the following Examples 8through 21, the alloy powder passes through a U. S. standard sieve of100 mesh, the pulverulent oxidant is an intimate interspersion of thestated metal oxides having an average particle size of about 1 to 5microns and the alloy powder-oxidant mixture is internally oxidized bythe method described in Parts D, E and F of Example 1. 1n the metaloxides presented in the following examples, copper is at a valence of 1,nickel is at a valence of 2, iron is at a valence of 3, silver is at avalence of 1, zirconium is at a valence of 4, molybdenum is at a valenceof 6 and beryllium and magnesium are at a valence of 2.

EXAMPLE 8 Dispersion-strengthened metal bar stock is formed by theabove-described method by oxidizing 100 parts of a powdered alloy of98.87 percent copper and 1.13 percent aluminum with 9.38 parts ofpulverulent oxidant comprising 9.2 parts of copper oxide and 0.18 partsof aluminum oxide. The resulting dispersionstrengthened bar stock hasincreased tensile strength and hardness at elevated temperatures orafter annealing as compared to bar stock of a similar copperaluminumalloy which has not been internally oxidized. Furthermore, thedispersion-strengthened bar stock does not have the disadvantages thatnormally result from compositional variations when the spent oxidant ispresent in the dispersion-strengthened workpiece.

EXAMPLE 9 Dispersion-strengthened metal bar stock is formed by theabove-described method by oxidizing 100 parts of a powdered alloy of99.37 percent copper and 0.63 percent beryllium with 10.26 parts ofpulverulent oxidant comprising 10.10 parts of copper oxide and 0.16parts beryllium oxide. I The resulting dispersionstrengthened bar stockhas increased tensile strength and hardness at elevated temperatures orafter annealing as compared to bar stock of a similar copperberylliumalloy which has not been internally oxidized. Furthermore, thedispersion-strengthened bar stock does not have the disadvantages thatnormally result from compositional variations when the spent oxidant ispresent in the dispersion-strenghtened workpiece.

EXAMPLE 10 Dispersion-strengthened metal bar stock is formed by theabove-described method by oxidizing 100 parts of a powdered alloy of99.90 percent copper and 0.10 percent zirconium with 0319 parts ofpulverulent oxidant comprising 0.318 parts of copper oxide and 0.001parts of zirconium oxide. The resulting dispersionstrengthened bar stockhas increased tensile strength and hardness at elevated temperatures orafter annealing as compared to bar stock of a similar copperzirconiumalloy which has not been internally oxidized. Furthermore, thedispersion-strengthened bar stock does not have the disadvantages thatnormally result from compositional variations when the spent oxidant ispresent in the dispersion-strengthened workpiece.

EXAMPLE 1 1 Dispersion-strengthened metal bar stock is formed by theabove-described method by oxidizing parts of a powdered alloy of 98.86percent nickel and 1.14 percent aluminum with 4.76 parts of pulverulentoxidant comprising 4.68 parts of nickel oxide and 008 parts of aluminumoxide. The resulting dispersion-strengthened bar stock has increasedtensile strength and hardness at elevated temperatures or afterannealing as compared to bar stock of a similar nickel-aluminum alloywhich has not been internally oxidized. Furthermore, thedispersiomstrengthened bar stock does not have the disadvantages thatnormally result from compositional variations when the spent oxidant ispresent in the dispersion-strengthened workpiece.

EXAMPLE 12 Dispersion-strengthened metal bar stock is formed by theabove-described method by oxidizing 100 parts of a powdered alloy of99.8 nickel and 0.2 percent beryllium with 1.687 parts of pulverulentoxidant comprising 1.680 parts of nickel oxide and 0.007 parts ofberyllium oxide. The resulting dispersion-strengthened bar stock hasincreased tensile strength and hardness at elevated temperatures orafter annealing as compared to bar stock of similar nickel-berylliumalloy which has not been internally oxidized. Furthermore, thedispersion-strengthened bar stock does not have the disadvantages thatnormally result from compositional variations when the spent oxidant ispresent in the dispersion-strengthened workpiece.

EXAMPLE 13 Dispersion-strengthened metal bar stock is formed by theabove-described method by oxidizing 100 parts of a a powdered alloy of99.8 percent nickel and 0.2 percent zirconium with 0.328 parts ofpulverulent oxidant comprising 0.327 parts of nickel oxide and 0.001parts of zirconium oxide. The resulting dispersionstrengthened bar stockhas increased tensile strength and hardness at elevated temperatures orafter annealing as compared to bar stock of similar nickelzirconiumalloy which has not been internally oxidized. Furthermore, thedispersion-strengthened bar stock does not have the disadvantages thatnormally result from compositional variations when the spent oxidant ispresent in the dispersion-strengthened workpiece.

EXAMPLE l4 Dispersion-strengthened metal bar stock is formed by theabove-described method by oxidizing 100 parts of a powdered alloy of98.72 percent iron and 1.28 percent aluminum with 3,864 parts ofpulverulent oxidant comprising 3.800 parts of iron oxide and 0.065 partsof aluminum oxide. The resulting dispersion-strengthened bar stock hasincreased tensile strength and hardness at elevated temperatures orafter annealing as compared to bar stock of a similar iron-aluminumalloy which has not been internally oxidized. Furthermore, thedispersion-strengthened bar stock does not have the disadvantages thatnormally result from compositional variations when the spent oxidant ispresent in the dispersion-strengthened workpiece.

EXAMPLE 15 Dispersion-strengthened metal bar stock is formed by theabove-described method by oxidizing 100 parts of a powdered alloy of99.55 percent iron and 0.45 percent beryllium with 2.724 parts ofpulverulent oxidant comprising 2.700 parts of iron oxide and 0.024 partsof beryllium oxide. The resulting dispersion-strengthened bar stock hasincreased tensile strength and hardness at elevated temperatures orafter annealing as compared to bar stock of a similar iron-berylliumalloy which has not been internally oxidized. Furthermore, thedispersion-strengthed bar stock does not have the disadvantages thatnormally result from compositional variations when the spent oxidant ispresent in the dispersion-strengthened workpiece.

EXAMPLE l6 Dispersion'strengthened metal bar stock is formed by theabove-described method by oxidizing 100 parts of a powdered alloy of99.04 percent silver and 0.96% aluminum with 12.70 parts of pulverulentoxidant comprising 12.48 parts of silver oxide and 0.22 parts ofaluminum oxide. The resulting dispersion-strengthened bar stock hasincreased tensile strength and hardness at elevated temperatures orafter annealing as compared to bar stock of a similar silver-aluminumalloy which has not been internally oxidized. Furthermore, thedispersion-strengthened bar stock does not have the disadvantages thatnormally result from compositional variations when the spent oxidant ispresent in the dispersionstrengthened workpiece.

EXAMPLE l7 Dispersion-strengthened metal bar stock is formed by theabove-described method by oxidizing 100 parts of a powdered alloy of98.84 percent silver and 1.16 percent magnesium with 11.30 parts ofpulverulent oxidant comprising 11.10 parts of silver oxide and 0.20parts of magnesium oxide. The resulting dispersionstrengthened bar stockhas increased tensile strength and hardness at elevated temperatures andafter annealing as compared to bar stock of a similar silvermagnesiumalloy which has not been internally oxidized. Furthermore, thedispersion-strengthened bar stock does not have the disadvantages thatnoramally result from compositional variations when the spent oxidant ispresent in the dispersion-strengthened workpiece.

Examples 18 and 19 illustrate the dispersion strengthening of alloys ofmatrix metals (rather than a single matrix metal) by internal oxidationusing the method of Examples 8 through 17.

EXAMPLE l8 Dispersion-strengthened metal bar stock is formed by theabove-described method by oxidizing 100 parts of a powdered alloy of72,54% copper, 26.33 percent nickel and 1.13 percent aluminum with 4.75parts of pulverulent oxidant comprising 4.67 parts of nickel oxide and0.08 parts of aluminum oxide. The matrix composition of the resultingdispersion-strengthened bar stock is 70.6 percent copper metal and 29.4per cent nickel metal. The resulting dispersionstrengthened bar stockhas increased tensile strength and hardness at elevated temperatures orafter annealing as compared to bar stock of a similarcopper-nickelaluminum alloy which has not been internally oxidized.Furthermore, the dispersion-strengthened bar stock does not have thedisadvantages that normally result from compositional variations whenthe spent oxidant is present in the dispersion-strengthened workpiece.

EXAMPLE l9 Dispersion-strengthened metal bar stock is formed by theabove-described method by oxidizing parts of a powdered alloy of 60.00percent nickel, 19.55 percent molybdenum, 20.00 percent iron and 0.45percent aluminum with 1.207 parts of pulverulent oxidant comprising1.200 parts of molybdenum oxide and 0.007 parts of aluminum oxide. Thematrix composition of the resulting dispersion-strengthened bar stock is59.5 percent nickel metal, 21.0 percent molybdenum metal and 19.5percent iron metal. The resulting dispersionstrengthened bar stock hasincreased tensile strength and hardness at elevated temperatures orafter annealing as compared to bar stock of a similarnickelmolybdenum-iromaluminum alloy which has not been internallyoxidized. Furthermore, the dispersionstrengthened bar stock does nothave the disadvantages that normally result from compositionalvariations when the spent oxidant is present in thedispersionstrengthened workpiece.

Examples 20 and 21 illustrate the dispersion strengthening of alloy ofmatrix metals and solute metals with an oxidant containing a hard,refractory oxide that is different from the solute metal oxide.

EXAMPLE 20 Dispersion-strengthened metal bar stock is formed by theabove-described method by oxidizing 100 parts of a powdered alloy of98.87 percent copper and 1.13 percent aluminum with 9.34 parts ofpulverulent oxidant comprising 9.20 parts of copper oxide and 0.14 partsof beryllium oxide. The resulting dispersion strengthened bar stock hasincreased tensile strength and hardness at elevated temperatures orafter anneal ing as compared to bar stock of a similar copperaluminumalloy which has not been internally oxidized. Furthermore, thedispersion-strengthened bar stock does not have the disadvantages thatnormally result from compositional variations when the spent oxidant ispresent in the dispersion-strengthened workpiece, although the dispersedoxides are dissimilar.

EXAMPLE 21 Dispersion-strengthened metal bar stock is formed by theabove-described method by oxidizing 100 parts of a powdered alloy of99.8 percent nickel and 0.2 percent zirconium with 0.329 parts ofpulverulent oxidant comprising 0.327 parts of nickel oxide and 0.002parts of aluminum oxide. The resulting dispersionstrengthened bar stockhas increased tensile strength and hardness at elevated temperatures orafter anneal ing as compared to the bar stock of similar nickelzirconiumalloy which has not been internally oxidized. Furthermore, thedispersion-strengthened bar stock does not have the disadvantages thatnormally result from compositional variations when the spent oxidant ispresent in the dispersion-strengthened workpiece, although the dispersedoxides are dissimilar.

Having thus described the invention, what is claimed 1. A process fordispersion-strengthening of metal by internal oxidation comprising:

providing a powdered alloy having an average particle size of less than300 microns comprising a matrix metal and a solute metal, said matrixmetal having a negative free energy of oxide formation at 25C. of up to70 kilocalories per gram atom of oxygen, said solute material having anegative free energy of oxide formation exceeding the negative freeenergy of oxide formation of said matrix material by at least about 60kilocalories per gram atom of oxygen at 25C.; providing an oxidantcomprising an intimate interspersion of in situ heat-reducible metaloxide and a finely divided hand refractory metal oxide, saidheat-reducible metal oxide having a negative free energy of formation at25C. of up to 70 kilocalories per gram atom of oxygen, said refractorymetal oxide having a negative free energy of formation exceeding thenegative free energy of formation of said heat-reducible metal oxide byat least about 60 kilocalories per gram atom of oxygen at 25C.;combining into an intimate mixture at least about 0.1

weight parts of said oxidant per 100 weight parts of said alloy, saidoxidant having the heat-reducible metal oxide present in at leaststoichiometric proportion for complete internal oxidation of all of saidsolute metal in said alloy; internally oxidizing said alloy mixed withsaid oxidant by heating to oxidize the solute metal of said alloy and toform a residue of said oxidant; and

thermally coalescing said internally oxidized alloy and said oxidantresidue into dispersionstrengthened metal stock.

2. The process of claim 1 wherein the ratio of the average particlediameter of the alloy particles to the average particle diameter of theoxidant particles is at least about 2:1.

3. The process of claim 1 wherein the metal moiety of said in situheat-reducible metal oxide is the same metal as said matrix metal.

4. The process of claim 3 wherein the metal moiety of said hard,refractory metal oxide is the same metal as said solute metal.

5. The process of claim 4 wherein the metal moiety of saidheat-reducible metal oxide and the metal moiety of said hard, refractorymetal oxide are in substantially the same proportion as the proportionof matrix metal and solute metal in said alloy.

6. The process of claim 1 wherein said solute metal is present in saidalloy in the proportion of 0.01 to 5 percent by weight of said alloy.

7. The process of claim 1 wherein said powdered alloy has an averageparticle size of less than about 150 microns.

8. The process of claim 7 wherein said powdered alloy has an averageparticle size of less than about 44 microns.

9. The process of claim 6 wherein the ratio of the av erage particlediameter of the alloy particles to the average particle diameter of theoxidant particles is between about 5:1 and about 30:l.

10. The process of claim 1 wherein said matrix metal is copper and saidsolute metal is aluminum.

11. The process of claim 5 wherein said matrix metal is copper and saidsolute metal is aluminum.

12. The process of claim 1 wherein about 0.1 to 10 weight parts of saidoxidant are mixed with 100 weight parts of alloy.

13. The process of claim 1 including the step of reducing said alloymixed with said oxidant with reducing gas after the step of internallyoxidizing the same.

14. A dispersion-strengthened metal produced by internally oxidizing amixture of 100 weight parts of a powdered alloy with at least about 0.1weight parts of an oxidant, said powdered alloy having an averageparticle size of less than 300 microns and comprising a relatively noblematrix metal having a negative free energy of oxide formation at 25C. ofup to kilocalories per gram atom of oxygen and a solute metal having anegative free energy of oxide formation exceeding that of said matrixmetal by at least about 60 kilocalories per gram atom of oxygen at 25C.,said oxidant comprising an intimate mixture of heat-reducible metaloxide having a negative free energy of formation at 25C. of up to 70kilocalories per gram atom of oxygen and finely divided refractory metaloxide having a neg ative free energy of formation exceeding the negativefree energy of formation of said heat-reducible metal oxide by at leastabout 60 kilocalories per gram atom of oxygen at 25C., saidheat-reducible metal oxide present in at least stoichiometricproportions for complete oxidation of all of said solute metal in saidalloy, comprising: a dispersion-strengthened metal mixture of oxidizedsolute metal, relatively noble matrix metal, residue of heat-reduciblemetal oxide, and hard refractory metal oxide, said mixture adapted to bethermally coalesced whereby said hard refractory metal oxide dispersionstrengthens said residue of heat-reducible metal oxide to formdispersion-strengthened metal stock.

15. The dispersion-strengthened metal mixture in claim 14 wherein saidmetal mixture is thermally coalesced and said residue of heat-reduciblemetal oxide is dispersion strengthened by said hard refractory metaloxide.

16. The dispersion-strengthened metal in claim 14 produced by internallyoxidizing a mixture of weight parts of said powdered alloy with fromabout 0.1 to l0 weight parts of said oxidant, and said metal moiety ofsaid residue of heat-reducible metal oxide is the same moiety as saidrelatively noble matrix metal.

17. The dispersion-strengthened metal in claim 16 wherein the metalmoiety of said hard refractory metal oxide is the same metal moiety assaid oxidized solute metal.

18. The dispersion-strengthened metal in claim 15 wherein the metalmoiety of said relatively noble matrix metal is copper and the metalmoiety of said oxidized solute metal is aluminum.

PO-105O QE TEFECATE @F CU i EQTIN Patent NO- 3.779. 714 Dated Decemberl8 1973 Inventor(s) Erhard Klar; Va Nadkarni It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Column 1, line 60, for "110" should read lOO-; Column 4, line 19, insert-Tin-; Column 8, line 67, for "99.2" should read 99.3; Column 10, line42, before "forged" insert ..-drop- Column 12, line 61, for "3,864"should read -3.865; Column 13, line 62, for "72,54%" should read-72.54%--; Column 15, line 19, for "hand" should read -hard-; Column 16,line 54, after "same" insert -metal.

Signed and sealed this 17th day of September 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer 6 Commissioner ofPatents 3333 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent 3.779.714 Dated DecemberlB, 1973 In 1 Erhard Klar; Anil V.Nadkarni It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 60, for "110" should read --lOO-; Column 4, line 19,insert --Tin-; Column 8, line 67, for "99.2" should read --99.3--;Column 10, line 42, before "forged" insert -droP-1-; Column 12, line 61,for "3,864" should read -3.86 5-; Column 13, line 62, for "72,54%"should read -72.54%--; Column 15, line 19, for "hand" should read hard-;Column 16, line 54, after "same" insert --metal--.

' Signed and sealed this 17th day of September 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents

2. The process of claim 1 wherein the ratio of the average particle diameter of the alloy particles to the average particle diameter of the oxidant particles is at least about 2:1.
 3. The process of claim 1 wherein the metal moiety of said in situ heat-reducible metal oxide is the same metal as said matrix metal.
 4. The process of claim 3 wherein the metal moiety of said hard, refractory metal oxide is the same metal as said solute metal.
 5. The process of claim 4 wherein the metal moiety of said heat-reducible metal oxide and the metal moiety of said hard, refractory metal oxide are in substantially the same proportion as the proportion of matrix metal and solute metal in said alloy.
 6. The process of claim 1 wherein said solute metal is present in said alloy in the proportion of 0.01 to 5 percent by weight of said alloy.
 7. The process of claim 1 wherein said powdered alloy has an average particle size of less than about 150 microns.
 8. The process of claim 7 wherein said powdered alloy has an average particle size of less than about 44 microns.
 9. The process of claim 6 wherein the ratio of the average particle diameter of the alloy particles to the average particle diameter of the oxidant particles is between about 5:1 and about 30:1.
 10. The process of claim 1 wherein said matrix metal is copper and said solute metal is aluminum.
 11. The process of claim 5 wherein said matrix metal is copper and said solute metal is aluminum.
 12. The process of claim 1 wherein about 0.1 to 10 weight parts of said oxidant are mixed with 100 weight parts of alloy.
 13. The process of claim 1 including the step of reducing said alloy mixed with said oxidant with reducing gas after the step of internally oxidizing the same.
 14. A dispersion-strengthened metal produced by internally oxidizing a mixture of 100 weight parts of a powdered alloy with at least about 0.1 weight parts of an oxidant, said powdered alloy having an average particle size of less than 300 microns and comprising a relatively noble matrix metal having a negative free energy of oxide formation at 25*C. of up to 70 kilocalories per gram atom of oxygen and a solute metal having a negative free energy of oxide formation exceeding that of said matrix metal by at least about 60 kilocalories per gram atom of oxygen at 25*C., said oxidant comprising an intimate mixture of heat-reducible metal oxide having a negative free energy of formation at 25*C. of up to 70 kilocalories per gram atom of oxygen and finely divided refractory metal oxide having a negative free energy of formation exceeding the negative free energy of formation of said heat-reducible metal oxide by at least about 60 kilocalories per gram atom of oxygen at 25*C., said heat-reducible metal oxide present in at least stoichiometric proportions for complete oxidation of all of said solute metal in said alloy, comprising: a dispersion-strengthened metal mixture of oxidized solute metal, relatively noble matrix metal, residue of heat-reducible metal oxide, and hard refractory metal oxide, said mixture adapted to be thermally coalesced whereby said hard refractorY metal oxide dispersion strengthens said residue of heat-reducible metal oxide to form dispersion-strengthened metal stock.
 15. The dispersion-strengthened metal mixture in claim 14 wherein said metal mixture is thermally coalesced and said residue of heat-reducible metal oxide is dispersion strengthened by said hard refractory metal oxide.
 16. The dispersion-strengthened metal in claim 14 produced by internally oxidizing a mixture of 100 weight parts of said powdered alloy with from about 0.1 to 10 weight parts of said oxidant, and said metal moiety of said residue of heat-reducible metal oxide is the same moiety as said relatively noble matrix metal.
 17. The dispersion-strengthened metal in claim 16 wherein the metal moiety of said hard refractory metal oxide is the same metal moiety as said oxidized solute metal.
 18. The dispersion-strengthened metal in claim 16 wherein the metal moiety of said relatively noble matrix metal is copper and the metal moiety of said oxidized solute metal is aluminum. 